Specifiying shape dimensions (size) when importing from CSV

[theorangeBirdybird]

I'd like to ask whether it is possible to specify shape's dimensions (size) when making diagraph from CSV file. I know that you can specify shape with #styles command, but I cannot specify it's dimensions this way.

I'm trying to construct activity diagram this way and a black rectangle symbolizing end of the fork isn't generated in the shape as I would like it to be.